Transistorized ignition system

ABSTRACT

An electrical system for use with an ignition system of the type including an ignition coil and breaker points. The electrical system provides for low current through the breaker points to minimize wear and corrosion of the breaker points, provides a high primary winding current at saturation of the primary winding and of the transistors of the electrical system to provide a strong spark, and has a minimum of components. The system includes first and second compound-connected transistors with the base of the second transistor being connected to the emitter of the first transistor and the collectors of said transistors being connected to ground potential. A voltage dividing circuit is adapted to be connected in series with the breaker points of a distributor between the emitter of the second transistor and the breaker points. The base of the first transistor is connected to a predetermined point in the voltage dividing circuit; and the emitter and collector of the second transistor are adapted to be connected in series with the primary winding of an ignition coil and a source of electric potential.

United States Patent 91 Cook [451 Oct. 16, 1973 TRANSISTORIZED IGNITIONSYSTEM [76] Inventor: William R. Cook, P. O. Box 1193,

Melrose Park, 111. 60161 [22] Filed: Feb. 22, 1971 [21] Appl. No.:117,378

[52] U.S. Cl. 123/148 E, 315/209 T 51 1m. (:1. F02p 3/02 [58] Field ofSearch 123/148 E; 315/209 T [56] References Cited UNITED STATES PATENTS3,640,260 2/1972 Mittag et a1 123/148 E 3,696,257 10/1972 Shano 123/148E 3,587,552 6/1971 Varaut 123/148 E 3,363,615 l/l968 Meyerle 123/148 E3,584,613 6/1971 Kreil 123/148 E 3,297,009 1/1967 Sasaki et a1. 123/148E 3,252,049 5/1966 Raybin 123/148 E 3,046,447 7/1962 Kirk et a1. 315/209T OTHER PUBLICATIONS Popular Electronics Transistor Ignition June, 1964.

Primary Examiner-Laurence M. Goodridge Assistant Examiner-Cort FlintAttorneyThomas R. Vigil [5 7] ABSTRACT An electrical system for use withan ignition system of the type including an ignition coil and breakerpoints. The electrical system provides for low current through thebreaker points to minimize wear and corrosion of the breaker points,provides a high primary winding current at saturation of the primarywinding and of the transistors of the electrical system to provide astrong spark, and has a minimum of components. The system includes firstand second compound-connected transistors with the base of the secondtransistor being connected to the emitter of the first transistor andthe collectors of said transistors being connected to ground potential.A voltage dividing circuit is adapted to be'connected in series with thebreaker points of a distributor between the emitter of the secondtransistor and the breaker points. The base of the first transistor isconnected to a predetermined point in the voltage dividing circuit; andthe emitter and collector of the second transistor are adapted to beconnected in series with the primary winding of an ignition coil and asource of electric potential.

8 Claims, 1 Drawing Figure Pmmnnnm as 1915 3.765. 391

INVENTOR WILL/AM R COOK @QMWJM Arm TRANSISTORIZED IGNITION SYSTEM Thisinvention relates to improvements and innovations in transistor circuitsfor use in transistorized ignition systems. More particularly, thepresent invention relates to an electrical system including twocompound-connected transistors for use in an ignition system.

Heretofore, a variety of transistorized ignition systems have beenproposed for use with an internal combustion engine such as the internalcombustion engine used in an automobile. In this respect, it has beenknown for some time that with a transistorized ignition system: a hotterspark across the electrodes of a spark plug can be obtained; a reductionin arcing across the breaker points in a distributor can be obtained,thereby reducing the maintenance normally required on the electricalignition system of the automobile; and a relatively constant outputvoltage across the secondary winding of the ignition coil at varyingengine speeds (RPM), and particularly at relatively high engine speeds,can be obtained.

A number of such known transistorized ignition systems are disclosed inthe Transistor Ignition Systems Handbook by Brice Ward, first printingJan. 19, 1966 by Howard W. Sams & C., lnc. Each of the knowntransistorized ignition systems typically includes a power transistorhaving the emitter and collector thereof connected in series with theprimary winding of an ignition coil and a source of electric potentialand having the base thereof connected to a point in a voltage dividingcircuit which is connected in series with the breaker points in thedistributor and with the source of electric potential. In the knowntransistorized ignition systems however, there is some drop-off in theoutput voltage of the secondary winding of the ignitioncoil at highengine speeds, some arcing across breaker points, and some fall off inthe maximum current through the primary winding of the coil and aresultant drop in spark energy at high engine speeds. It is desirabletherefore, to provide an improved transistorized ignition system whichoperates more efficiently with respect to output voltage, breaker pointarcing, and spark energy. Accordingly, it is a primary object of thepresent invention to provide such an improved transistorized ignitionsystem.

Another object of the present invention is to provide an electricalsystem which is adapted for use in an electrical ignition system and inwhich a minimum of components are used providing a very reliablecircuit.

Another object of the present invention is to provide an electricalsystem which is adapted for use in an electrical ignition system whichutilizes a transistor circuit including two compound-connectedtransistors.

Another object of the present invention is to provide an improvedtransistorized ignition system which provides a relatively constantoutput voltage at the secondary winding of an ignition coil through awide range of engine speeds.

Another object of the present invention is to provide a transistorizedignition system which greatly minimizes, if not altogether eliminates,arcing across the breaker points in a distributor of an electricalignition system used with an internal combustion engine.

Another object of the present invention is to provide an improvedtransistorized ignition system which maintains a hot spark across theelectrodes of a spark plug by maintaining high current flow through theprimary winding'of an ignition coil at high engine speeds.

Another object of the present invention is to provide a transistorizedignition system including two compound-connected transistors which acttogether as one transistor requiring a very small trigger or turn onsignal and having a very small drop off of collector current fromemitter current at saturation of the one transistor.

Another object of the present invention is to provide a transistorcircuit for use in an electrical ignition system, with the circuitproviding for very stable operation of the ignition system and providinga relatively constant output voltage and current to the spark plugsthrough a wide range of engine speeds.

Another object of the present invention is to provide an electricalsystem for use in an electrical ignition system for an internalcombustion engine and which electrical system is of simple and compactdesign so that the electrical system can be simply installed without theneed for special skills and with a minimum of tools.

Still another object of the present invention is to provide anelectrical system which includes a transistor circuit and which can besimply connected into the electrical ignition system for an internalcombustion engine by merely connecting two leads into the ignitionsystem circuit and by connecting a heat sink chassis mounting theelectrical system to ground potential.

In accordance with one preferred embodiment of the invention, there isprovided an electrical system for use in an ignition system of the typeincluding an ignition coil and distributor breaker points, theelectrical system including first and second compound-connectedtransistor each having a base and first and second output terminals, andmeans for applying a signal to the base of the first transistor. Thebase of the second transistor is connected to the first output terminalof the first transistor, the second output terminal of the firsttransistor is connected to the second output terminal of the secondtransistor, and the first and second output terminals of the secondtransistor are adapted to be connected in series with the ignition coiland a source of electric potential.

For a more complete understanding of the nature and scope of the presentinvention reference will now be had to the accompanying schematicdrawing of the electrical system of the present invention.

Referring now to the drawing, an electrical ignition system is generallyindicated at 10 and the electrical system of the present invention,which is adapted for use in and forms a part of the system 10, isgenerally indicated at 12.

The ignition system 10 also includes an ignition coil 14, a ballastresistor 16 and a single pole triple throw switch 18 having threestationary contacts 18a, 18b and 18c and one movable contact 20. Theswitch 18 is typically a key operated ignition switch of the typenormally found in an automobile. As shown in the drawing, a line 22 froma suitable source of electric potential, such as a 12 volt battery, isconnected to the movable contact 20 of the switch 18. When the movablecontact 20 is in a first position engaging the contact 18a, the switch18 is in the off position. When it engages the contact 18b, the switch18 is in the running position with a circuit established between theline 22 and the ballast resistor 16 through the switch 18; and when thecontact 20 engages the contact 18c, the switch 18 is in the startposition with a circuit established between the line 22 and a lead 24which by-passes the ballast resistor 16 and is connected to the ignitioncoil 14.

The ignition coil 14 is of known construction and includes a'primarywinding 28 and a secondary winding 30. As shown, the lead 24 and theballast resistor 16 are connected to one end 28a of the primary winding28. The other end 28b is connectd to one end 30a of the secondarywinding 30. The other end 30b of the secondary winding 30 is adapted tobe connected to one electrode of a conventional spark plug (not shown).

As shown in the drawing, the electrical system 12 of the presentinvention has three terminals or leads generally indicated at 31, 32 and33. Preferably, the electrical system 12 is mounted on a heat sinkchassis which, being metal, can take the place of, or constitute, lead32. In this way, the electrical system can be assembled and sold as acomplete package with two leads extending from the chassis forconnection into a conventional ignition system to form the ignitionsystem 10. In this respect, the lead 31 is adapted for connection to oneend, end 28b of the primary winding 28, the leadchassis-32 is adaptedfor connection to a common or ground conductor which is connected to thesource of electrical potential, i.e., to one side of the battery, andthe lead 33 is adapted for connection to one side of a set of breakerpoints 34 in a distributor (not shown) forming part of the ignitionsystem 10.

The system 12 includes first and second compoundconnected transistors 41and 42. The transistor 41 has a base 41b and first and second outputterminalsemitter and collector-41c and 410. Likewise, the transistor 42has a base 42b and first and second output terminals-emitter andcollector-42e and 42c. As shown, the base 42b of the second transistor42 is connected to the emitter 41c of the first transistor 41 and thecollector 41c of the first transistor 41 is connected to the collector42c of the second transistor 42. The emitter 42e of the secondtransistor 42 is connected to the lead 31 and the collector 42c of thesecond transistor 42 is connected to the lead 32. In this way, when theelectrical system 12 is connected into and forms part of the ignitionsystem 10, the emitter and collector 42e and 42c of the secondtransistor 42 will be connected in series with the primary winding 28 ofthe ignition coil 14.

The electrical system 12 also includes a voltage dividing circuit formedby resistors R and R which are connected between leads 31 and 33. Asshown the base 41b of the transistor 41 is connected to a junction 44between the resistors R and R In other words, the resistor R, isconnected between the emitter 42e of the second transistor 42 and thebase 41b of the first transistor 41, and the second resistor R isconnected between the base 41b of the first transistor 41 and the lead33 adapted to be connected to breaker points 34.

has not been heretofore proposed. The electrical system 12 of thepresent invention, by utilizing compoundconnected transistors providesseveral advantages over known transistorized ignition systems. In thisrespect, the drop off of collector current at high emitter currentsthrough the second transistor 42 is very small. As a result, the coil 14can be connected between the source and the system 12 or between thesystem 12 and ground with the current flowing through the primarywinding 28 being essentially the same for either connection. Also, byusing a primary winding having a small current rise time and by usingcompoundconnected transistors which are quickly saturated, theoperatingcharacteristics of the system 10 are maintained relativelyconstant even at high engine speeds resulting in the obtainment of a hotspark (spark energy) through a wide range of engine speeds.Additionally, the compound-connected transistors 41 and 42 act as asingle transistor with very high gain. As a result, only a very smallsignal need be applied to the base 41b of the first transistor 41 inorder to trigger or turn on the transistor 41 to turn on the transistor42.

Moreover, by including two compound-connected transistors and a voltagedividing circuit consisting in the resistors R and R the electricalsystem 12 operates with a very small electrical current through thebreaker points 34 and there is very little, if any, arcing across thebreaker points 34 when they are opened or closed. In this way, pittingor corrosion of the breaker points 34 is avoided.

In one preferred embodiment of the electrical system 12 and as shown inthe drawing, a capacitor 46 is connected across the emitter 42e andcollector 42c of the second transistor 42. The capacitor 46 functionsmainly as an AC shunt for transient signals or currents which may bepicked up by the ignition system 10. ln particular, upon collapse of themagnetic field induced in the ignition coil 14, the capacitor 46 willabsorb any current generated in the primary winding 28. As a result, itis very likely that a charge will be placed on the capacitor 46 afterthe breaker points 34 are opened and the induced magnetic fieldcollapses.

Although the actual operation of the system 12 is not known withcomplete certainty, it is believed that any charge accumulated or placedon the capacitor 46 will assist and enhance the operation of the circuit12 par- The compound connecting of transistors has been J ticularly athigh engine speeds. In this respect, it will be understood that theignition coil 14 is initially in a steady state (zero field) conditionand will resist a change in its state. Therefore, when the breakerpoints 34 are closed the inherent tendency of the coil 14 to resist achange in the state of the magnetic field therein will momentarilyimpede the flow of current through the primary winding 28 and throughthe resistors R and R Thus, a very slight time lag in the flow ofcurrent through resistors R and R may be incurred if the capacitor 46 isnot connected in the circuit. It is believed that by having thecapacitor 46 in the system 12 when the breaker points 34 are closed, acurrent path is immediately established through resistors R and R forthe discharge of any current charge stored in the capacitor 46, and itis believed that this current will be sufficient to establish a signalof sufficient magnitude at the base 41b of the first transistor 41 forimmediately turning on the first transistor 41 to turn on the secondtransistor 42. Accordingly, it is believed that the charging of thecapacitor 46 upon each collapse of the field in the coil 14, and thedissipation of this charge through the resistors R and R ensures andprovides for immediate turn on of the transistors 41 and 42 to ensuresaturation of the coil 14 to maintain a hot spark (high spark energy)through a wide range of engine speeds.

Also, in one preferred embodiment of the electrical system 12 of thepresent invention and as shown in the drawing, a zener diode 48 isconnected across the emitter 42c and collector 42c of the secondtransistor 42. The zener diode 48 has a break down voltage which is lessthan the maximum permissible collector-emitter voltage for thetransistor 42, and its primary purpose is to protect the secondtransistor 42 from over-voltages in a well known manner.

Since, as described above, there is very little drop off between theemitter and collector currents through the transistor 42, the ballastresistor 16 and the ignition coil 14 can be connected between groundpotential and the lead 32, as generally indicated by phantom lines at-50. However, the circuit connections described above are preferred sincethey simplify the assembly of the electrical system 12 and theconnection thereof into an ignition system to form the system 10. Inthis respect the collectors 41c and 420 can be simply connected to theheat sink (metal) chassis on which the transistors 41 and 42 arepreferably mounted. Then the ground connection, indicated by the lead 32in the drawing, is effected through the chassis which can be easilysecured to the metal frame supporting the internal combustion engine. Inthis way, there are only two leads, the leads 31 and 33, from theelectrical system 12 which need to be connected as shown. If thecollectors were notcon.- nected to ground, they would have to beinsulated'from ground and the third lead 32 would then be connected tothe collectors 41c and 42 c.

By reason of the compact circuit connections in the electrical system 12and by having only two output leads 31 and 33, the preferred embodimentof the electrical system 12 of the present invention canbe readily andsimply installed with a minimum of tools and without requiring specialskills. In this respect, a simple instruction sheet for installing theelectrical, system 12 in an automobile will instruct one (a) to securelymount the heat sink to the chassis of the automobile, (b) to break theconventional connection between the coil and the breaker points, (c) toconnect the lead31 to one side of the primary winding of. the ignitioncoil and (d) to connect the lead 33 to the breaker points.

In one working example of the ignition system l0.utilizing theelectrical system 12 of the present invention, the values of the circuitelements of the ignition system were as follows:

Ballast resistor 16 0.5 ohms (150 watts) Resistor R 10 ohms (1 watt)Resistor R 10 ohms 11 watts) Capacitor 46 2 microfarads (150 WVDCElectrolytic) Zener diode 48 Motorola IN3004 (91 Volts BreakdownVoltage) Transistors 41 and 42 -Motorola 2N2834 (20 Amp,

V 100 Volts) Ignition coil 14 400:1 Turns ratio (Low Primary WindingInductance 40 KV Output Voltage) The ignition system 10 is cyclicallyoperated with each cycle being initiated by the closing of the breakerpoints 34. As soon as the breaker points 34 are closed,

current flows through the resistors R and R from either the capacitor 46and/or the voltage source. When a signal of sufficient magnitude isestablished at the base 41b of the transistor 41, the transistor 41 istumed on to turn on the transistor 42, i.e., to allow current to flowthrough the emitter base junction of the transistor 42 and the emittercollector of the transistor 41 to turn on the transistor 42. When thetransistor 42 is rendered conducting, current flows through the primarywinding 28 of the coil 14 until the breaker points 34 are opened atwhich time the field in the coil 14 collapses and produces a sparkacross the electrodes connected to the ends of the secondary winding 30of the coil 14.

Although one preferred embodiment of the electrical system 12 of thepresent invention has been described it is to be understood that obviousmodifications or variations can be made to the electrical system 12 ofthe present invention without departing from the scope of the invention.In this respect it is to be understood that the electrical system 12 canoperate without the capacitor 46 and the diode 48 bearing in mind, ofcourse, that the possibility of damage to the transistors 42- and 41- isappreciably increased by the removal of these protective circuitelements. Additionally, a diode can be connected between the emitter 42cand the resistor R, as shown in phantom lines at 54 for preventinginverse currentflow through the resistors R and R and for limitingpowerlosses in the transistors 41and 42. Another variation would be toeliminate the connection between the ends 28b and 30a of the windings 28and 30 of the coil 14, connect the end 30a to ground, and then connect arelatively large resistor between the end 28b of the primary winding 28and ground, to permit a small amount of current to flow through theprimary winding at all times. Accordingly, the scope of the presentinvention is only to be limited as necessitated by the accompanyingclaims.

I claim:

I. A transistorized ignition system including, in combination, atransformer coil having a primary winding anda secondary winding, firstand second compoundconnected transistors each having a base and firstand second output terminals, said first output terminal of said firsttransistor being connected to said base of said second transistor, saidsecond output terminal of said first transistor being connected to saidsecond output terminal of said second transistor, and said outputterminals of said second transistor being connected in series with theprimary winding of said transformer, a voltage dividing circuitconnected between said first output terminal of said second transistorand one terminal of a set of breaker points in a distributor, the baseof said first transistor being connected to a point in said voltagedividing circuit, and a capacitor connected across said output terminalsof said second transistor in such a manner that, when the breaker pointsare closed and before the transistors conduct, a closed loop seriescircuit is formed for discharging any charge on said capacitor, saidloop consisting of said capacitor, said voltage dividing circuit and thecommon conductor for said system.

2. The system of claim 1 including a zener diode connected across saidoutput terminals of said second transistor.

3; The system of claim 1 wherein said coil is con- I nected to saidfirst output terminal of said second transistor and is adapted to beconnected to a source of electric potential.

4. The system of claim 1 wherein said voltage dividing circuit includesa first resistor connected between said first output terminal of saidsecond transistor and the base of said first transistor and a secondresistor connected between the base of said first transistor and saidbreaker points.

5. The system of claim 1 including a ballast resistor connected inseries with said primary winding of said coil.

6. An electrical system for use with an ignition system of the typeincluding an ignition coil, said electrical system including first andsecond compound-connected transistors each having a base and first andsecond output terminals, means adapted to be connected between theignition coil and a cyclical switching device and connected to said baseof said first transistor for cyclically applying a signal to said baseof said first transistor, said base of said second transistor beingconnected to said first output terminal of said first transistor, saidsecond output terminal of said first transistor being connected to saidsecond output terminal of said second transistor, said first and secondoutput terminals of said second transistor being adapted to be connectedin series with the ignition coil and a source of electric potential saidsignal applying means consisting of a first impedance connected betweensaid first output terminal of said second transistor and the base ofsaid first transistor and a second impedance connected to said base ofsaid first transistor and adapted to be connected to a cylical switchingdevice, and a capacitor connected across said output terminals of saidsecond transistor in such a manner that, when the switching device isclosed and before the transistors conduct, a closed loop series circuitis formed for discharging any charge on said capacitor, said loopconsisting of said capacitor, said first impedance, said secondimpedance and the common conductor for said system.

7. The electrical system of claim 6 including a zener diode connectedacross said output terminals of said second transistor.

8. An electrical system for use with an ignition system of the typeincluding an ignition coil, said system including first and secondcompound-connected transistors, the emitter and collector of said secondtransistor being adapted to be connected in series with the ignitioncoil and a source of electric potential, the emitter of said firsttransistor being connected to the base of said second transistor, thecollector of said first transistor being connected to the collector ofsaid second transistor, a resistor connected between the emitter of saidsecond transistor and the base of said first transistor, a resistorconnected to said base of said first transistor and adapted to beconnected to a cyclical switching device, a capactior connected acrosssaid emitter and collector of said second transistor in such a mannerthat, when the switching device is closed and before the transistorsconduct, a closed loop series circuit is formed for discharging anycharge on said capacitor, said loop consisting of said capacitor, saidresistors and the common conductor for said system, and a zener diodeconnected across said emitter and collector of said second transistor.

1. A transistorized ignition system including, in combination, atransformer coil having a primary winding and a secondary winding, firstand second compound-connected transistors each having a base and firstand second output terminals, said first output terminal of said firsttransistor being connected to said base of said second transistor, saidsecond output terminal of said first transistor being connected to saidsecond output terminal of said second transistor, and said outputterminals of said second transistor being connected in series with theprimary winding of said transformer, a voltage dividing circuitconnected between said first output terminal of said second transistorand one terminal of a set of breaker points in a distributor, the baseof said first transistor being connected to a point in said voltagedividing circuit, and a capacitor connected across said output terminalsof said second transistor in such a manner that, when the breaker pointsare closed and before the transistors conduct, a closed loop seriescircuit is formed for discharging any charge on said capacitor, saidloop consisting of said capacitor, said voltage dividing circuit and thecommon conductor for said system.
 2. The system of claim 1 including azener diode connected across said output terminals of said secondtransistor.
 3. The system of claim 1 wherein said coil is connected tosaid first output terminal of said second transistor and is adapted tobe connected to a source of electric potential.
 4. The system of claim 1wherein said voltage dividing circuit includes a first resistorconnected between said first output terminal of said second transistorand the base of said first transistor and a second resistor connectedbetween the base of said first transistor and said breaker points. 5.The system of claim 1 includIng a ballast resistor connected in serieswith said primary winding of said coil.
 6. An electrical system for usewith an ignition system of the type including an ignition coil, saidelectrical system including first and second compound-connectedtransistors each having a base and first and second output terminals,means adapted to be connected between the ignition coil and a cyclicalswitching device and connected to said base of said first transistor forcyclically applying a signal to said base of said first transistor, saidbase of said second transistor being connected to said first outputterminal of said first transistor, said second output terminal of saidfirst transistor being connected to said second output terminal of saidsecond transistor, said first and second output terminals of said secondtransistor being adapted to be connected in series with the ignitioncoil and a source of electric potential said signal applying meansconsisting of a first impedance connected between said first outputterminal of said second transistor and the base of said first transistorand a second impedance connected to said base of said first transistorand adapted to be connected to a cyclical switching device, and acapacitor connected across said output terminals of said secondtransistor in such a manner that, when the switching device is closedand before the transistors conduct, a closed loop series circuit isformed for discharging any charge on said capacitor, said loopconsisting of said capacitor, said first impedance, said secondimpedance and the common conductor for said system.
 7. The electricalsystem of claim 6 including a zener diode connected across said outputterminals of said second transistor.
 8. An electrical system for usewith an ignition system of the type including an ignition coil, saidsystem including first and second compound-connected transistors, theemitter and collector of said second transistor being adapted to beconnected in series with the ignition coil and a source of electricpotential, the emitter of said first transistor being connected to thebase of said second transistor, the collector of said first transistorbeing connected to the collector of said second transistor, a resistorconnected between the emitter of said second transistor and the base ofsaid first transistor, a resistor connected to said base of said firsttransistor and adapted to be connected to a cyclical switching device, acapactior connected across said emitter and collector of said secondtransistor in such a manner that, when the switching device is closedand before the transistors conduct, a closed loop series circuit isformed for discharging any charge on said capacitor, said loopconsisting of said capacitor, said resistors and the common conductorfor said system, and a zener diode connected across said emitter andcollector of said second transistor.